Fluid handling systems offering corrosive resistance and high purity have many applications in advanced technologies. These applications include solar, LED, flat panel display technologies and in the semiconductor industry for applications such as photolithography, bulk chemical delivery, chemical mechanical polishing, wet etch and clean. In order to provide the corrosive resistance, inert properties are required for high purity applications. Current fittings for such liquid handling systems are made from perfluoroalkoxy alkane (PFA), ethylene tetrafluoroethylene (ETFE), fluorinated ethylene propylene (FEP). Besides providing non-corrosive and inert construction, many fluoropolymers, such as PFA, are injection moldable.
Several types of connector fittings are available and are known as PRIMELOCK® fittings and pillar fittings and typically connect a tubing end shaped to be bulbous with and utilizing a ring shaped spacer. PRIMELOCK® is a registered trademark of Entegris, Inc., of Billerica, Mass., U.S.A., owner of the present application.
While the use of melt processible resins has provided the inertness, resistance and the ability to mold components of fluid handling systems to just about any shape or size, the tensile strength and compressive strength of the material is lower than conventional metal used for fittings. For example, the tensile strength of PFA is 24 MPa (megaPascals, or 106 Pascals), of FEP is 23 MPa, and of ETFE is 40-46 MPa. In contrast, the tensile strength of 316 stainless steel is 276 MPa. Fittings on plumbing components have a nut which is tightened on the body of the fitting. The fitting body is typically an integral or unitary part of a plumbing component or equipment such as a T, a reducer, an elbow, a valve, a filter, a measurement device, or other equipment or apparatus. Often, particularly for larger fittings, in order to tighten the nut, the body must be secured. Conventionally, this may be provided by flats on the body that will receive the parallel faces of a conventional open-ended wrench. The flats may be part of a hex with the shape of a conventional nut or be two flats where the fitting body is part of a “T” fitting for example. Typically the flats are spaced apart on the body a distance of 20 to 60% of the diameter of the interior fluid flow conduit. Particularly for larger PFA fittings, such as for 1½ inch flow conduits or greater, the high torque forces required to tighten fittings, which are typically 250 ft-lbf or greater, together with the inherent slipperiness and the easy compressibility of the material, utilizing such conventional wrenches to secure the body may cause the wrench to slip off of the body, potentially damage the body, and/or make adequate tightening of the fitting problematic.
Improved fittings and tightening appurtenances and methods for larger polymer couplings would be a welcomed contribution.